"Thor: The Dark World," for those keeping score at home, is the eighth installment in Marvel Films' game-changing, ridiculously profitable superhero franchise that started with 2008's "Iron Man" and hit its peak (so far) with 2012's billion-dollar-earning "The Avengers." By now, unsurprisingly, the Marvel folks have the formula for super-success down pat.

And so in "Thor: The Dark World," as in all the films in the "Avengers" family, we get eye-popping action sequences set around enormous set pieces, and we get a host of noble, strong-jawed heroes determined to protect puny Earthlings from an outsized, otherwordly threat. We also get a charming, game cast for whom the ability to deliver a well-timed one-liner is a chief job requirement.

So it was in the "Iron Man" films. So it was in "Captain America." So it was in the first "Thor" and "The Avengers."

And given how much coin each of those films made at the box office, so it is in "Thor: The Dark World," a sequel to 2011's "Thor" and a film that dutifully follows that framework. On one hand, that adherence to the Marvel blueprint assures comic-book fans a certain level of production quality. These movies, after all, aren't ones to scrimp in the budget department. On the other hand, a formula is a formula.

Granted, Marvel Films has used those eight outings to construct brilliantly a multi-layered superhero universe in which various characters cross over into other films. (This includes an amusing appearance by one of Thor's fellow Avengers midway through "Dark World.") Unfortunately, they've not been quite as ambitious in the bar-raising department.

As a result, for all of its production value -- including fantastic, award-worthy costumes by Wendy Partridge -- "Thor: The Dark World" often lapses into a certain ho-humness. It's all built around so much clanging of swords and denting of armor, but lacking that spark of life that made so many people sit up and take notice when "Iron Man" essentially reinvented the superhero genre five years ago.

Instead, we get a light comedy, wrapped in an action film, inside a dense, muddled Norse-tinged mythology -- and all of it swathed in a regal red cloak that would make Lando Calrissian jealous.

It's directed by longtime television helmer Alan Taylor, whose impressive career has been built largely on his direction of episodes of such prestige series as "The Sopranos" (for which he won an Emmy), "Mad Men," "Sex and the City," "The West Wing" and "Homicide: Life on the Streets." It's his work on HBO's medieval fantasy drama "Game of Thrones," however, that most informs "Thor: The Dark World." He begins the film with a muddy, bloody battlefield scene set to a Very Serious Voiceover by Odin himself (Anthony Hopkins) to establish the underlying mythology.

That mythology, for the record, involves an ancient race known as Dark Elves (spoiler: they're not the singing, toy-making kind) who want desperately to get their hands on an all-powerful weapon called the Aether. This weapon will serve them in their ongoing efforts to destroy all that is good and shiny.

Their cause is helped by the fact that the Nine Realms -- of which our Earthly dimension is one -- are on the verge of a once-in-5,000-years alignment that opens portals between all nine. As cool as that sounds, it becomes a problem when Dark Elf leader Malekith (Christopher Eccleston) decides to use it to further his nefarious plans.

It also sucks Thor's Earthbound squeeze, Jane Foster (Natalie Portman), into the mix, making things personal for the hammer-wielding one, played once more by Chris Hemsworth. (Fate? Or a ridiculous contrivance from a script all too willing to indulge in them? I'll let you decide.)

Brainy Jane is an astrophysicist -- a fact that persuaded Portman to take the role in the first "Thor" movie -- but don't hold onto any delusions that she's a strong female character. Rather, at least in this outing, she's an annoyingly old-fashioned damsel in distress who is entirely passive until the final few minutes after the film already has devolved into a third-act maelstrom of numbing visual effects.

At least her wiseacre intern Darcy Lewis (Kat Dannings) is there once more to provide a dash of comic relief. Also helping in that regard is Thor's black-sheep brother, Loki (Tom Hiddleston), who is as unpredictable a movie villain as there is, and therefore is the most interesting character in the film.

Even with him, "Thor: The Dark World" plays like a film more intended to please the comic-book faithful than to win over newcomers. That's true right down the first of two "hidden" scenes embedded in the closing credits -- a Marvel Films hallmark -- which stars Benicio Del Toro and which would appear to set up a future "Avengers" adventure. (The second hidden scene, though lighter, comes at the very end, after all the credits have scrolled by, so sit tight after the movie.)

None of that is to say that "Thor: The Dark World" is a bad movie, necessarily. I would never speak ill of a man with a giant, magical hammer. At the same time, hammer or no hammer, it doesn't quite nail it, either.

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THOR: THE DARK WORLD2 stars, out of 5

Snapshot: A superhero sequel in which the
hammer-wielding Thor must embark on a journey to defeat a marauding army
of Dark Elves that not even the great Odin can match.

What works: All the expected Marvel Films flourishes
are present and accounted for, including a strong cast, lush sets and
costumes, and great visual effects.

What doesn't: The mythology-rich story becomes more muddled the longer the film goes on, devolving into a numbing third-act maelstrom.